Department of Radiology, The University of Chicago, Chicago, IL, USA.
Department of Radiation and Cellular Oncology, The University of Chicago, Chicago, IL, USA.
J Xray Sci Technol. 2021;29(6):975-985. doi: 10.3233/XST-210974.
Interest exists in dual-energy computed tomography (DECT) imaging with scanning arcs of limited-angular ranges (LARs) for reducing scan time and radiation dose, and for enabling scan configurations of C-arm CT that can avoid possible collision between the rotating X-ray tube/detector and the imaged subject.
In this work, we investigate image reconstruction for a type of configurations of practical DECT interest, referred to as the two-orthogonal-arc configuration, in which low- and high-kVp data are collected over two non-overlapping arcs of equal LAR α, ranging from 30° to 90°, separated by 90°. The configuration can readily be implemented, e.g., on CT with dual sources separated by 90° or with the slow-kVp-switching technique.
The directional-total-variation (DTV) algorithm developed previously for image reconstruction in conventional, single-energy CT is tailored to enable image reconstruction in DECT with two-orthogonal-arc configurations.
Performing visual inspection and quantitative analysis of monochromatic images obtained and effective atomic numbers estimated, we observe that the monochromatic images of the DTV algorithm from LAR data are with substantially reduced LAR artifacts, which are observed otherwise in those of existing algorithms, and thus visually correlate reasonably well, in terms of metrics PCC and nMI, with their reference images obtained from full-angular-range data. In addition, effective atomic numbers estimated from LAR data of DECT with two-orthogonal-arc configurations are in reasonable agreement, with relative errors up to ∼ 10%, with those estimated from full-angular-range data in DECT.
The results acquired in the work may yield insights into the design of LAR configurations of practical dual-energy application relevance in diagnostic CT or C-arm CT imaging.
使用具有有限角度范围（LAR）的扫描弧的双能计算机断层扫描（DECT）成像具有降低扫描时间和辐射剂量的兴趣，并能够实现 C 臂 CT 的扫描配置，从而避免旋转 X 射线管/探测器与成像对象之间可能发生的碰撞。
在这项工作中，我们研究了一种实用的 DECT 感兴趣的配置的图像重建，称为两个正交弧配置，其中低千伏和高千伏数据分别在两个不重叠的相等 LARα的弧上收集，范围从 30°到 90°，相隔 90°。该配置可以很容易地实现，例如在双源分离 90°的 CT 或使用慢千伏切换技术的 CT 上。
为了在常规的单能 CT 中进行图像重建而开发的方向全变差（DTV）算法经过定制，能够在具有两个正交弧配置的 DECT 中进行图像重建。
通过对获得的单色图像进行视觉检查和定量分析，并估计有效原子数，我们观察到 DTV 算法从 LAR 数据获得的单色图像具有明显减少的 LAR 伪影，而在现有算法的图像中观察到了这些伪影，因此在基于度量 PCC 和 nMI 的视觉上与从全角范围数据获得的参考图像相当吻合。此外，从具有两个正交弧配置的 DECT 的 LAR 数据估计的有效原子数与从 DECT 的全角范围数据估计的有效原子数之间具有合理的一致性，相对误差高达约 10%。
这项工作中的结果可能为诊断 CT 或 C 臂 CT 成像中实用的双能应用相关的 LAR 配置的设计提供一些思路。
